How do I kill the process using port 873?

On macOS & Linux, run: "sudo systemctl stop rsync || sudo killall rsync". On Windows PowerShell (as Admin), run: "Stop-Process -Name rsync -Force -ErrorAction SilentlyContinue".

Why am I getting "port 873 already in use" (EADDRINUSE)?

This occurs when another background instance of rsync, rsyncd or a zombie process is already bound to port 873. Use the kill commands above to free the port immediately.

DevOps & Cloud

Risk: Medium

Port 873 — rsync Remote Sync Daemon

Q: Is Port 873 safe to expose to the public internet?

Risk level is Medium. Rsync daemon authentication can be weak if rsyncd.secrets is misconfigured. In most modern infrastructures, rsync over SSH (port 22) is preferred.

Port 873 is the default TCP port for the rsync daemon (rsyncd), facilitating high-speed differential file synchronization and server backups across networks.

PORT NUMBER

873

PROTOCOL

TCP

DEFAULT PROCESS

rsync, rsyncd

FIREWALL TARGET

873/tcp

Instant Terminal Fixes for Port 873

macOS & Linux Terminal

1. Check who is listening on port 873:

sudo lsof -i :873 || sudo ss -tulpn | grep ":873 "

2. Kill process occupying port 873 (EADDRINUSE fix):

sudo systemctl stop rsync || sudo killall rsync

3. UFW Firewall Allow rule:

sudo ufw allow from 192.168.1.0/24 to any port 873 proto tcp

Windows PowerShell (Admin)

1. Check listening port:

Get-NetTCPConnection -LocalPort 873

2. Force kill process on port 873:

Stop-Process -Name rsync -Force -ErrorAction SilentlyContinue

3. Docker Port Forwarding Mapping:

docker run -d -p 873:873 -v /data:/data servercontainers/rsync

Common Error Encountered

rsync: failed to connect to host (port 873): Connection refused.

Security Advisory & Hardening

Rsync daemon authentication can be weak if rsyncd.secrets is misconfigured. In most modern infrastructures, rsync over SSH (port 22) is preferred.

Frequently Asked Questions

Port 873 Questions & Answers

Common questions regarding default services, kill commands, and firewall configurations.

Port 873 is commonly used for rsync Remote Sync Daemon. Port 873 is the default TCP port for the rsync daemon (rsyncd), facilitating high-speed differential file synchronization and server backups across networks.

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